New Mexico Geological Society Annual Spring Meeting — Abstracts

Fault-related slip deformation and diagenesis alter the permeability of the parent sedimentary basin fill by changing the pore size distribution and interconnectedness. These alterations allow fault zones to act as either barriers or conduits to ground-water flow. The importance of fault zone controls on permeability in well-indurated sedimentary rocks is well known in reservoir engineering because faults often seal or compartmentalize hydrocarbon reservoirs. However, fault-zone impacts on the permeability of poorly consolidated sediments typical of aquifers are not wen understood. Field measurements of gas permeability at two faulted outcrops of Santa Fe Group sediments indicate that fault-related changes decrease permeability within the fault zone relative to that for the parent basin fill material. Geostatistical analysis is employed to determine whether the permeability decreases are significantly distinguishable from the naturally-occurring permeability heterogeneity of the parent materials. Thin-section petrography is used to examine how the permeability changes are related to a hierarchy of structural deformations and to post-slip diagenetic changes.